Rhubarb juice as a natural antibrowning agent

To search for natural antibrowning agents, rhubarb juice was tested on fresh-cut apple slices and found to have a potent effect. Liberty apple slices were treated in various concentrations of rhubarb juice (5% - 100%), and the rate of discoloration at room temperature was measured by a Hunter Colorimeter. Apple slices treated in the 5% - 10% solution showed browning activity with δL values of 2.3 - 2.5 at two hours. However, the concentrations of rhubarb juice above 20% inhibited apple browning effectively with no change in the L value for several hours. Analysis of oxalic acid in rhubarb juice showed that the 20% solution contained about 67 mg/100g.